Date: Wed, 10 Jan 2018 15:24:42 -0500 From: Mark Johnston <markj@FreeBSD.org> To: Warner Losh <imp@FreeBSD.org> Cc: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r326964 - head/sys/cam Message-ID: <20180110202442.GC78524@raichu> In-Reply-To: <201712190413.vBJ4DMY9090982@repo.freebsd.org> References: <201712190413.vBJ4DMY9090982@repo.freebsd.org>
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On Tue, Dec 19, 2017 at 04:13:22AM +0000, Warner Losh wrote: > Author: imp > Date: Tue Dec 19 04:13:22 2017 > New Revision: 326964 > URL: https://svnweb.freebsd.org/changeset/base/326964 > > Log: > When doing a dump, the scheduler is normally not running, so this > changed worked to capture dumps for me. However, the test for > SCHEDULER_STOPPED() isn't right. We can also call the dump routine > from ddb, in which case the scheduler is still running. This leads to > an assertion panic that we're sleeping when we shouldn't. Instead, use > the proper test for dumping or not. This brings us in line with other > places that do special things while we're doing polled I/O like this. > > Noticed by: pho@ > Differential Revision: https://reviews.freebsd.org/D13531 > > Modified: > head/sys/cam/cam_periph.c > > Modified: head/sys/cam/cam_periph.c > ============================================================================== > --- head/sys/cam/cam_periph.c Tue Dec 19 04:06:07 2017 (r326963) > +++ head/sys/cam/cam_periph.c Tue Dec 19 04:13:22 2017 (r326964) > @@ -38,6 +38,7 @@ __FBSDID("$FreeBSD$"); > #include <sys/malloc.h> > #include <sys/kernel.h> > #include <sys/bio.h> > +#include <sys/conf.h> > #include <sys/lock.h> > #include <sys/mutex.h> > #include <sys/buf.h> > @@ -1158,7 +1159,7 @@ cam_periph_runccb(union ccb *ccb, > struct bintime *starttime; > struct bintime ltime; > int error; > - bool sched_stopped; > + bool must_poll; > struct mtx *periph_mtx; > struct cam_periph *periph; > uint32_t timeout = 1; > @@ -1182,7 +1183,13 @@ cam_periph_runccb(union ccb *ccb, > devstat_start_transaction(ds, starttime); > } > > - sched_stopped = SCHEDULER_STOPPED(); > + /* > + * We must poll the I/O while we're dumping. The scheduler is normally > + * stopped for dumping, except when we call doadump from ddb. While the > + * scheduler is running in this case, we still need to poll the I/O to > + * avoid sleeping waiting for the ccb to complete. > + */ > + must_poll = dumping; Hmm, unfortunately this introduces a new problem: after a panic we call adashutdown() as part of the shutdown_post_sync event. This occurs before we call doadump(), so dumping == 0 and we don't poll for the spindown command's completion. But since we've panicked, the scheduler is stopped, and so we just hang.
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